Green synthesis of furan di-Schiff bases via a one-pot tandem amination-oxidation-amination process under room temperature

Abstract

Furan-based double Schiff bases (DRIF), multifunctional molecules derived from biomass, were possessed significant application potential in various fields including sensors, stabilizers, dyes, and pharmaceuticals. The synthesis of DRIF typically involves a series of steps: amination, oxidation, and subsequent amination. However, this process could encounter side reactions such as overoxidation, aldol condensation, and cross-oligomerization. Herein, an efficient TEMPOL/Cu(NO₃)₂ catalytic system for one-pot process with 5-HMF and n-butylamine as model reactant to produce 2,5-di(butyliminomethyl)furan (DBIF) at room-temperature was developed. Characterization techniques including FT-IR, ESI-MS, GC-MS, and ¹H NMR were employed to identify key intermediates and reaction mechanisms. The maximum DBIF yield of 97 % was attained. Furthermore, the study extended the amine oxidation amination reactions using HMF and furfural with various primary amines, demonstrating good substrate compatibility. Ultimately, a one-pot two-step method was successfully employed to obtain a total yield of 63 % DBIF from fructose, further highlighting the application potential of this catalytic system.